An example is here. In this case the answer is mine, but that is not the point. It just reappeared as Community 13 (is that how many times it has reappeared?). In this case, OP commented a couple times, may have been helped, but it shows up again. Could we make it that moderators could tag things as answered, not to show up again automatically? I tend to upvote answers that are on the robo reappear to stop this. Comments on that?
(13 is the current rep of Community.)
If no one votes up any of the answers, and no answer is accepted, then I think it is good for the question to be bumped once in a while. If there is a good answer, then someone should vote it up eventually, and this exposure will help it occur sooner, hopefully. If there is not a good answer, then occasionally bringing more attention to the question is a good idea in general.
I don't think that there should be a special "answered" tag, because a single answer with a positive vote count (or an accepted answer) is already enough to remove the question from the Unanswered list and to stop the periodic bumping by Community. If there is an answer that users feel renders the placement on the Unanswered list inappropriate, then users can vote up the answer. Sometimes it takes a while, especially for questions that very few people care enough about to read enough to determine whether the answers are in fact good answers. In the meantime, I don't think the bumpings are a real problem.